A problem presented by the arrangement described above is that it functions most properly when the radio connection between the base station system and the subscriber terminal is balanced, in other words radio signals travel regularly and symmetrically in both directions. The problem in radio connections comprising sporadic and/or asymmetrical traffic is that, because a long time may have elapsed since the reception of a previous signal from the subscriber terminal, the angle of departure does not necessarily correspond to the actual location of the subscriber terminal. During this time, the subscriber terminal may have moved too much for the signal transmitted using the angle of departure formed on the basis of the old angle of incidence to reach the subscriber terminal. The properties of the channel used in the radio connection also change on account of the change in the location. A next signal received by using an out-of-date angle of incidence and transmitted by the subscriber terminal can also be lost.
The problem is serious particularly in cellular radio networks using packet transmission; in a typical packet transmission, one party, for example the base station system, transmits much data, and the subscriber terminal possibly only transmits occasional retransmission requests. The use of a WWW (World Wide Web) browser, for example, results in heavy traffic on the downlink and light traffic on the uplink.